The present invention relates to an auxiliary switch block for attachment to a basic device, in particular a contactor.
A generic auxiliary switch block is obtainable on the electrical market. Auxiliary switch blocks of this type, as well as the basic devices, are provided with normally-closed and normally-open contacts.
Satisfactory normally-closed and normally-open functioning presupposes forcible guidance of the auxiliary switch block in relation to the basic device. This is ensured if, in the event of welding of a normally-closed contact in the auxiliary switch block, there is still an air gap of at least 0.5 mm at the normally-open contacts of the basic device.
Maintaining forcible guidance within a device, that is to say within an auxiliary switch block or a basic device, normally does not represent a problem. If the basic device and the auxiliary switch block are accommodated in a common housing, the coupling tolerances that occur here can be eliminated, and the forcible guidance can also be ensured here. However, the forcible guidance is made more difficult if an auxiliary switch block is subsequently attached to a basic device, as is illustrated in FIG. 2. In this case, the difficulty with the forcible guidance results from the fact that the contact carrier is guided only by relatively closely adjacent points of contact in the region of the interrupter chamber (see FIG. 3), which can result in a correspondingly exaggerated oblique position of the contact carrier. This tilted position can be transmitted to the coupled contact-piece carrier of the basic device and, in the event of welding of a normally-closed contact, together with the coupling tolerances of the auxiliary switch block in relation to the basic device, may result in an inadequately large air gap at one of the normally-open contacts.
European Patent No. 045 683 describes a single-pole auxiliary switch that can be coupled to a contactor. The contact carrier (of elongate design) of the auxiliary switch carries only a single contact piece, and is movably guided in an interrupter chamber. Here, the aim of guiding the contact-bridge carrier is merely the movement of the contacts between the open and closed positions. Because of the single-pole design, however, it is not necessary here to have any additional forcible guidance, such as is needed for a plurality of contact pieces which are located alongside one another under unfavorable conditions.
An object of the present invention is to improve an auxiliary switch block to the effect that the necessary forcible guidance is achieved.
According to the present invention, the object is achieved in that the contact carrier is provided, opposite the coupling point, with an extension which extends over the entire height of said carrier, reaches into a region of the interrupter chamber projecting beyond the contact carrier, and engages with guide means of the interrupter chamber in this region.
The auxiliary switching block has, on a side by which it is attached, a coupling point to engage with a contact carrier of the basic device, and has two rows of windows which are located one above another and each of which, in operation, is occupied by a contact piece only in the upper or lower window, depending on the design as a normally-closed or normally-open function, the height of the contact carrier essentially corresponding to the height of the pairs of windows.